Incorrect Calculation of Buffer Size Affecting kernel6.12-modules-extra-common package, versions <1:6.12.103-127.188.amzn2023


Severity

Recommended
0.0
high
0
10

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.51% (42nd percentile)

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  • Snyk IDSNYK-AMZN2023-KERNEL612MODULESEXTRACOMMON-19476683
  • published1 Sept 2026
  • disclosed10 Aug 2026

Introduced: 10 Aug 2026

CVE-2026-68388  (opens in a new tab)
CWE-131  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel6.12-modules-extra-common to version 1:6.12.103-127.188.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2110.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel6.12-modules-extra-common package and not the kernel6.12-modules-extra-common package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

smb/client: handle overlapping allocated ranges in fallocate

smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC.

The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset.

For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200):

    Request:      [100, 400)
    Server range: [  0, 200)  allocated

Correct:
[100, 200)    allocated data, skip
[200, 400)    hole, zero-fill

Current:
[100, 300)    skipped
[300, 400)    zero-filled afterwards

The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled.

Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows.

This also prevents a malformed range length from causing an out-of-bounds zero-buffer read.

CVSS Base Scores

version 3.1